How should a Christian deal with tithing and taxation?

The most common principle about the tithing rate is 10%.
However, tax rates are not all equal worldwide.
Where I live, the highest marginal tax rate is about 48%.
If I were to give 48% of my income to the government (plus paying 15% taxes on products I buy, plus paying general government fees, etc.) AND 10% of tithe... there wouldn't be much left, compare to someone whose tax rate is much lower.
It is easier for a less-taxed person to tithe the 10% then for a high-taxed person.
Therefore, how should a Christian deal with tithing and tax rates?

When we use the word “tithing” it only refers to the OT Law of tithing and has nothing to do with the NT Church! I won't indulge in this to much other than if you follow the tithing law today bc a Church leader is teaching this or its something you believed since you were young than I encourage you to please read all of malachi 3 and look at the whole picture and not take this out of context as most do. Be a Berean!
Paul told us to be “cheerful givers.” 2nd Cor 9:6-15
As far as comparing the tithing law with paying taxes, we cannot!
"give back to Caesers what is Caesers and to God what is God's" Matthew 22
God never commanded us to give 10% or any % in the NT. God does command us to pay taxes though! What we give to God has to come from our heart not a command. What we must pay Caeser, pay it, whether the tax rate is 10% or 48%- taxes have no bearing on what we give to God! Just as it says in Matthew chapter 22.
This is difficult for most, like myself I was also taught the "tithing law" and lived by it for years til God's HS made me aware of the unbiblical teaching of the "luke warm" Church of today. So trying to seperate oneself from all the lies that we held onto for years is hard to do but we must be "overcomers" - walk with the HS and follow God and not the ways of the world.

There is no question that the Bible instructs us to pay our taxes. But I believe the New Testament leaves the question of the tithe open because God wants us to be joyful and free givers from the heart. I don't think it is helpful to put yourself under a rule in this matter, unless it is one you are convicted of by the Holy Spirit and can joyfully embrace.
I was not taught to tithe in my Church as a young person. Several years ago The Lord began to deal with my heart about giving. He showed me a need. The amount that the person needed "happened" to be exactly 10% of a recent bonus. That experience was repeated once more and I began joyfully setting aside 10% of my net income. As I began to experience the joy of giving into the kingdom I switched to tithing from the gross because I wanted to have more impact for Him.
I also live in a high tax rate area (similar to you). I have had less money problems and more financial blessing since I began walking in obedience to what The Lord showed me to do.

The Bible refers to tithing as giving back to God one tenth of your income.
Malachi 3:8-12
Will man rob God? Yet you are robbing me. But you say, ‘How have we robbed you?’ In your tithes and contributions. You are cursed with a curse, for you are robbing me, the whole nation of you. Bring the full tithe into the storehouse, that there may be food in my house. And thereby put me to the test, says the Lord of hosts, if I will not open the windows of heaven for you and pour down for you a blessing until there is no more need. I will rebuke the devourer for you, so that it will not destroy the fruits of your soil, and your vine in the field shall not fail to bear, says the Lord of hosts. Then all nations will call you blessed, for you will be a land of delight, says the Lord of hosts.
Tithing is a command from God. When you get your pay check, you have to tithe 10% of it as your income increases so does your tithe. Once you file your taxes, then you have to pay 10% of your tax return. The only reason why you do not have to pay your tithe when you get your tax return is when you paid you tithe not only on the pay check that lands in your hand BUT on your total Gross, that is your total income without tax or other contributions having been deducted. It takes a lot of faithfulness to God to be able to do this. Also paying of first fruit is always rewarded by God.

Because few Christians have actually studied the tithe laws and most denominations which teach tithing do so from selfish motivation there is little understanding in the church concerning how the tithe was to be handled according to the Old Covenant form of the law. No one I am aware of examines how this law is to be interpreted under the New Covenant.
In her response to Tiffany's answer Jennifer Goss states that Malachi 3:6-10 that this passage speaks of the priest's theft of God's tithe. She also states this in another thread on this subject. I have never heard this assertion before and have never done a detailed study of this passage so I cannot really state whether she is accurate or not. However, I can state unequivocally that in the denominations that teach tithing today I am not aware of a single one where the clergy is not stealing the tithe and is not diverting it from God's stated and intended purpose.
As I stated in the previously mentioned other thread, scripture is very clear that the primary purpose of the tithe is to support the Levites, not the priests. The Levites were also required to tithe and their tithe went to the priests. The denomination in which I was raised (and most others I am aware of) restricts the tithe to the payment of pastor's salaries. This is simply an incorrect disbursement of these funds.
Although the priests were Levites they were a separate class, and the only tithe funds that go to the priests is the tithes given by the rest of the Levites. The rest of the Levites were not allowed to serve as priests, and although most were associated with temple service in auxiliary roles, the Levites were not necessarly tasked to those "religious" duties.
In Numbers 4 we find that the Levites redeemed the first born sons of the nation of Israel in the same manner as the lambs that were required (Exodus 13:11-13). Israel was God's firstborn son (Exodus 4:22, 23) and the Levites were the "firstborn" of Israel by redemption. The role of the firstborn was both priestly and governmental, so it is understandable how the priests would think the tithe belongs to them. But the Levites were intended to be the judges in all the towns and cities, as well as any other governmental function existing in those cities and towns, to serve as the healers, the musicians, the teachers, the record keepers (deeds, titles, birth records) and the attorneys in Israel as well. The tithe is given to these people as their inheritance (Numbers 18:21, 24, 26) and then pass their own tithe on to the priests (Numbers 18:28) As such, the tithe is a tax to support both the civil and religious governments in Israel. Many denominations point to verse 28 claiming that it means we should give a second tithe in addition to the one we give to the priests. This is simply greed on the part of Priests/Pastors. Ezekiel 34 has much to say about such shepherds over God's flock.
Deuteronomy 14 gives further, more detailed instructions concerning the tithe, and who is to be supported by it. Many denominations point to this as being yet another (second or third) tithe that God requires of us. However Deut 14:29 is key to interpreting this passage. The tithe is given to the Levites because they have no inheritance in Israel and along with them three other classes which have no inheritance are named -- foreigners (symbolism for unbelievers) widows and the fatherless. God claims all of these as his inheritance to be fed from his table. Of course, those who eat from his table are expected to do his work. How many denominations do you know who provide for these "disinherited" people in this way? In all too many the tithe is used simply as an excuse for the pastor to get rich.
Under the New Covenant all these laws take on a different form. I have never spent much time studying how this is to be applied under the New Covenant, but I do know that God wants much more than just our money.